Ankle-Brachial Index (ABI)
The ankle-brachial index is ankle blood pressure divided by arm blood pressure. When the vessels supplying the legs narrow, ankle pressure drops relative to the arm and this number falls.
Your numbers
Ankle-brachial index (ABI)
1.08
What it means
1.08 is within the normal range (0.9–1.4).
Formula
Ankle-brachial index (ABI) = Ankle systolic pressure (mmHg) ÷ Arm systolic pressure (mmHg)
This is a reading aid, not a diagnosis. Real measurement follows a set protocol with a Doppler device across both arms and both ankles.
What to enter
| Input | Default | Accepted range |
|---|---|---|
| Ankle systolic pressure (mmHg) (mmHg) | 130 | 50 ~ 250 |
| Arm systolic pressure (mmHg) (mmHg) | 120 | 50 ~ 250 |
Step by step
Quick reference table
Results when only Ankle systolic pressure (mmHg) (mmHg) changes and everything else stays put.
| Ankle systolic pressure (mmHg) (mmHg) | Ankle-brachial index (ABI) |
|---|---|
| 65 | 0.54 |
| 97.5 | 0.81 |
| 130 | 1.08 |
| 195 | 1.63 |
| 250 | 2.08 |
What each result means
| Result | At default values |
|---|---|
| Ankle-brachial index (ABI)Ankle blood pressure divided by arm blood pressure; flags narrowed blood flow in the legs. | 1.08 |
Common mistakes
This is a reading aid, not a diagnosis. Real measurement follows a set protocol with a Doppler device across both arms and both ankles.
Frequently asked questions
QHow is Ankle-Brachial Index (ABI) calculated?
Ankle-brachial index (ABI) = Ankle systolic pressure (mmHg) ÷ Arm systolic pressure (mmHg) — The ankle-brachial index is ankle blood pressure divided by arm blood pressure. When the vessels supplying the legs narrow, ankle pressure drops relative to the arm and this number falls.
QCan you walk through an example?
With Ankle systolic pressure (mmHg) 130mmHg, Arm systolic pressure (mmHg) 120mmHg, the answer is Ankle-brachial index (ABI) 1.08.
QWhat do I need to enter?
Enter Ankle systolic pressure (mmHg), Arm systolic pressure (mmHg). The result recalculates as you type, and an empty box counts as zero.
QHow much does the answer move if I change a number?
Changing only Ankle systolic pressure (mmHg) (mmHg) moves the answer to Ankle systolic pressure (mmHg) (mmHg) 65 → Ankle-brachial index (ABI) 0.54 and Ankle systolic pressure (mmHg) (mmHg) 250 → Ankle-brachial index (ABI) 2.08. The table below lays out five steps.
QHow are the numbers rounded?
Money is shown to the nearest whole unit, percentages to one decimal place and everything else to two. What you see is rounded; the calculation itself carries the unrounded value forward.
QAnything to watch out for?
This is a reading aid, not a diagnosis. Real measurement follows a set protocol with a Doppler device across both arms and both ankles.
Related calculators
These calculators help you understand health figures; they do not replace diagnosis or prescription. See a clinician if you have symptoms.